Wave-transmission system



Nov. 3, 1925.

E. V. GRIGGS WAVE TRANSMI SS ION SYSTEM Filed Aug. 2.9, 1919 3 Sheets-Shee //7 vex? for:

f/mer M G/v'yys.

Patented Nov. 3, 192 5.

um'rao STATES I 1,559,867 PATENT OFFICE.

m V. GRIGGS, OF EAST ORANGE, NEW JERSEY, ASSIGNOB TO WESTERN ELMTBIC COMPANY, INCORPORATED, OF NEW YORK, N, Y., A CORPOBAT IOK 0] NEW YORK.

WAVE-TRANSMISSION SYSTIM.

Application filed August 29, 1819. Serial No. 320,553.

To all whom it may concern:

Be it known that I, Emma V. Games, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Wave- Transmission Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to transmission systems and methods of transmission and more particularly to Systems and methods for the transmission of signals b the use of carrier waves. In systems 0 this type, the energy of low frequency or slgnahng current is utilized to modulate the energy of higher frequency or carrier currents which are transmitted to a remote station and there detected by means of a detecting devlce which reproduces currents having a wave form or other characteristic or characteristics so related to the original signaling wave as to be available for the reproduction of the signal. In accordance with the invention a single device is provided for modulating outgoing and detecting incoming carrier waves in systems of this type.

One object of the invention viewed broadly may be stated to be the provision of a duplex system wherein reversible and 1nterchangeable devices, having symmetr cal conductivity, are provided for transferring in each direction the energy to be transmitted.

Another object is the provision of suitable forms of devices which may be connected in such a system to act either as a modulator or as a detector according to Whether the energy is being transmitted or received.

Another object is to rovide reversible and interchangeable devlces which, when connected at any point in a signaling system by suitable transformers or equivalent means, will serve as a modulator for waves passing in one direction and as a detector for Waves passing in the other direction irrespective as to which terminal of the device is connected to the low frequency side of the line.

In systems containingthermionic amplifiers, modulators or detectors, imperfect operation sometimes results from singing or the generation of undesired oscillations in some part of the system. Means are here 1rovided to eliminate or reduce this trou- Since an important advantage of carrier current systems over ordinary transmission systems is the facility with which they lend t emselves to multip ex communication several arrangements for multiplexing are erein shown and constitute an important part of the invention. Plural or successive modulation systems utilizing various novel features of the invention are also described herein.

A further object is that of roviding novel forms of cord circuits whereby multilexing may be facilitated and particulary whereby subscribers lines may be conveniently and interchangeably connected to trunk lines. The modulator-detectors herein described are under certain circumstances, included in the cord circuits.

Another object is to provide reversible thermionic repeating systems requiring no space current sources,- other than the waves to be transmitted and suitable carrier frequency generators.

Among the important advanta es, peculiar to signaling, of systems uti izing the principles hereinafter described is that of reducing the necessity for balancing line impedances and the necessity for the provision of conjugate arrangements of incoming and outgoing low and high frequency circuits with respect to each other.

In general, the rinciples of the invention will be descri (1 herein mainly with reference to telephone systems, since telephony is the more comprehensive form of signaling, the principles of which apply to telegraphy and other less specialized forms of transmission in which the reproduction of a definite wave form is not essential. As used herein the word line will be understood to include any long or short conductive circuit either loaded or unloaded which may be adapted for the requirements of a particular installation. Certain features of the invention are of general application as, for example, to radio transmission and other electrical systems as well as to signaling over conductive circuits and hence will be claimed broadly. In particular, the fundamental idea of using a sin le apparatus to modulate outgoing and detect incoming waves is adapted for radio communication.

For this purpose a pair of radiating conductors, one at each station and D, may be substituted for the line 2.

The invention will be more fully described in connection with the accompanying drawings wherein Fi 1 is a diagrammatic rep resentation of t e essential features of a duplex system in accordance with the invention; Fig.2 a more detailed diagram of I the modulator-detector stations G and D of Fig. 1; Fi 2 shows a air of antennae which may substituted or the high frequency line; Fi 3 shows an arrangement or multiplex signaling; Fig. 4 a modified form for plural modulation multiplex signaling; Fig. 5 a modified form of modulator-detector circuit; Fig. 6 a slight modification of the circuit arrangement of Fig. 5; Figs. 7, 8 and 9 are other modified forms of modulator-detector circuits.

Referrin to Fig. 1, A and B are subscribers su stations which typify any two points between which telephonic communication is to be established. Voice currents of speech frequency, hereinafter called signalin currents, will be produced at station A and transmitted over a local line 1 to station 0, where modulated electrical waves or currents are produced and transmitted over a high frequency line 2 to the station D and there detected to produce electrical waves similar to those produced at the station A which are transmitted over the local line 3 to the station B for the reproduction of the original signals. The apparatus at stations C and D are duplicatesas may be seen by reference to Fig. 2 where they are shown in greater detail.

Referring to Fig.. 2, apparatus C o y will be described at length from which escription the duplicate apparatus D will be readily understood. The apparatus C is herein styled a modulator-detector and consists of a carrier frequency generator G symmetrically connected through the coils 8 to the two pairs of uni-directionally conducting two electrode thermionic discharge tubes 4, 5, 6 and 7. Each tube preferably comprises a suitable hi hly evacuated ,contaimng envelope, 9. eated filamentary cathode and an anode. Normall the generator G will not cause any hig freuency currents to be transmitted either to t e line 2 or the line 1 owin to the balanced relation of the coils 8 wit respect to the tubes, the lines, and the generator G, the latter being connected to the electrical midpoint of each coil. When, however, a current flowing in the line 1 causes an electromotive force to be induced in the coils 8 in a particular direction, the resulting unbalance of the current throu h the coils 8 will cause a modulated high equency current to be impressed upon the line 2. In accordance with known princi les, current in the line 2 will consist of w at has previously been &

currents it may be taken as typicalof the various sinusoidal waves into which the.

speech current at a given instant may be resolved. i

The pure modulated wave will be transmitted to the station D and the frequencies 11+: and 2-8 will there be combined with a wave of frequency p locally generated by the generator G which will result in'a detected current being transmitted to the line 3 which current will, as one component thereof, include .a current or wave of the frequency a. This current upon traversing the line 3 will be received at the station D to affect a receiving. instrument in the usual manner to reproduce the sound of the original si al. Space current sources 10 may be inc uded in the circuits of the tubes comprising the apparatus C. The sources 10 of each pair of tubes 4 and 5 are op sitely directed with respect to generator The sources 10 are not essential to render the system operative and maybe considered to be of zero terminal voltage and ne ligible resistance. 10 are of substantial and equal voltage and produce a normal space current throu h the tubes whenno signals are passing. T 0 apparatus C and the apparatus D are interchangeable, symmetrical, reversible, and doubly functioning in that they will modulate currents to be transmitted and detect received, modulated currents and reproduce therefrom the original signal, providedthe generators G have the same or substantially the same frequency. The transformers of which the coils 8 form a part may have any Preferably, however, t e sources winding ratios which will be desirable in particular instances. Re at' a paratus of this type which will pa s ell l gy in either direction constitutes an un rtant feature of the invention. Fi 2 i ustrates how antennae 2 ma be en tituted for the conductive line 2. ach antenna will be connected to its respective station G or D. The windings of the transformers 8 which are included in the line in Fig. 2 will be included in the antennas 2'. In this manner any of the arrangements herein described may be used for radio sigalin by substituting wave radiating and absor ing antenna systems for the high frequency line.

Fig. 3 il ustrates one manner of using the devices of Fi 2 for multiplex transmission over the big frequency or trunk line 2. The a paratus shown corresponds to the stations and C. Duplicate apparatus will be provided at the stations D and B which are located at the remote terminus of the line 2. Line 2 is typical of any desired number of trunk lines which may terminate at distant stations similar to station D. Several circuits, such as shown at station C (Fig. 2) are included in the respective cord circuits at station 0 (Fig. 3). The cord circuits each include all the apparatus connected therein between the connecting jacks 11. will each produce a different frequency. In the present instance the fre uencies are 10,000, 20,000, 30,000 respective y, the word frequencies being used throughout this specification to indicate the number of cycles per second.

Now suppose a subscriber at one of the stations A, A or A desires to communicate with a subscriber B. Upon calling the operator at C by any suitable calling or signaling means and advising her of his desire, the operator at C selects an idle cord circuit at that station and notifies the operator at D to call the particular subscriber B and connect him to the trunk line 2 by means of a cord circuit at the station B having a generator G of the particular carrier frequency which the operator at C desires to use. The cord circuit having the generator G" with a frequency of 30,000 may be supposed to be selected and the subscriber A, A or A as the case may be, is connected to the line D through that circuit. When subscriber A talks, the speech waves transmitted over the line 1 cause pure modulated waves to be transmitted over the line 2 to the station B where they are detected and thence are received by the subscriber B to re roduce the sounds of the voice of the su scriber A. Conversely the subscriber B can talk with the subscriber A in a similar manner through the same circuits and energy-transferring devices. Monitoring at the stations C and D may be done by a monitoring circuit MC connected to the low frequency side of the line. If, however, the operators monitoring circuit contains a detector, the monitoring may be accom lished by connecting the monitoring circuit C to the high frequency side of the line. While as many cord circuits are illustrated as there are lines 1, a great many local lines 1 may be served by a comparatively few cord circuits.

Fig. 4 represents an arrangement adapted for the transmission of plurally modulated waves. A, A and A" are subscribers stations and A a telegraphic station. The cord circuits preferably terminate in plugs adapted for connection to jacks 11 and contain filters F, F, F" and F which are adapted to transmit the respective bands of frequencies indicated thereon. M, M, M" and M are circuits such as shown at G The generators G in the cord circuits (Fig. 2), or their equivalents, having generators producing the carrier frequencies indicated thereon. F,, F, F," F," are also band filters adapted to transmit the bands of frequencies respectively indicated thereon. M, is a circuit such as shown at C (Fig. 2) having its generator-frequency indicated thereon and is a band filter adapted to pass the band of frequencies from 68,000 to 132,000 as indicated.

The transmission of speech signals through a single one of the cord circuits in each direction will serve to explain the operation of this arrangement. For the purpose of this specification, it will be assumed that transmission of the band of frequencies from 200 to 2,000 will enable reproduction of speech of a sufliciently good quality and that higher and lower frequencies may be eliminated. Suppose the subscriber A is connected to the cord circuit containing the modulator M, then speech currents produced in the line 1 connected to the substation A will'be transmitted throu h the filter F to the modulator M which wil cause the transmission of a correspondingly pure modulated wave through the filter F, to the modulator M, which includes a enerator constantly producing the carrier requency 100,000 as indicated. From the modulator M, there willbe transmitted through the filter F to the line 2, a pure modulated wave having the base frequency 100,000 and,

from 10,000 to 12,000 according to whetherthe upper or lower side-frequency band is to be eliminated. Telegraphy may be simultaneously carried on from or to one or more stations A'. When considered in connection with the symbols on the drawings, the

operations of transmitting and receiving tele raphic signals will be clear without furt er description. The carrierfrequencies which are herein sug sted are illustraioo tive only and other suita 1e values, may be selected. Likewise the various filters may be designed to ass such ranges of frequencies an to exc ude such frequencies as may be found most desirable in practice. Other modulators such as M, may beconnected to the line 2, each modulator M, being provided with a different carrier frequency and being connected to the line through a suitable filter, while at a remote point on line 2 similar communicating stations having the same carrier frequency are provided.

Figs. 5 to 9 inclusive represent forms of modulator-detector circuits which may, if desired, be substituted for that shown at (J gig. 2). Referrin' particularly to Fig. 5, t e ow fr uency me 1 ma be connected with or wit out the interposition of a jack out ut circuits of the repeaters 14 are psitely connected to the primary of atransrmer 16 whosesecondary has its terminals connected across the line. The filter F is included in the line, the. opposite terminal of this filter-being ad'acent the line 2. The terminal element of ter F comprises a low impedance path for high frequency currents passing through the primaries 12. This arrangement serves to modulate low fr uency currents which are generated in the inc .1 or to detect high frequency modulated currents whose base frequency is 50,000 which. are received through the line 2. This apparatus may be substituted for one of the cord circuits shown in Figs. 3 or 4 and the operation will be analogous to the operation of the devices of those cord circuits as heretofore, iven.

In 1g. 6 a resistance or impedance 17 is shunted acrow the lineand from mid-point of this resistance a conductor 18 extends which may be connected to the filamentary cathodes of a 'pair of repeaters, such as shown in Fi 5. Other conductors 19 may be connect to the impedance-controlling elements of the repeaters. The secondary of the transformer 16 will, in this case, be included in circuit with a primary 20 of a transformer whose secondary 21 may consist of one or more coils serially included in the line in a manner similar to the coils 12 (Fig. The arrangement of Fig. 6 will likewise receive low frequency currents from the line 1 and transmit modulated waves from which the unmodulated com nent of carrier frejrpliency has been eliminated, to the line 2, t

e reverse action taking place in a case where the modulated waves are received from the line 2.

The arran ment shown in Fig. 7 differs from that o 'Fi 5 in having a single repeater 14 inste of a duplex repeating arrangement comprising a pair of repeaters 14. With a single tube or repeater, no provision is made for eliminating the carrier frequency component from the outgoing modulated current. If it is desired not to transmit the carrier frequency component the filter F may be designed to pass only the range of fr uencies each case eliminating p. or example, the transmitted band mightbe either 10,200 to 12,000 or 8,000 to 9,800 where the carrier frequency, 12, is 10,000. Coil 13 is coupled to coils 12. Coil 13 is included in the input circuit of tube 14. The generator typifies any convenient source of voltage of a suitable carrier fre uency, for example, 10,000 cycles. The mo ulated current in the output c1rcuit is impressed upon the line 2 throu h the transformer "-16 and the filter F,. ncoming current/is detected in a similar manner, the low frequency component being. impressed upon the line 1 through transformer 16 and the filter F. The band filters F and F pass only the range of frequency indicated."

Fig. 8 represents a further modified form of the arrangement of Fig. 5. The circuit 22 is connected to one secondary 23 of transformer 16 and feeds detected signaling frequency energy to the line 1 through the filter F... The feed back connection of the circuit 22 is on the side of the filter F which is connected to the line 1. An at tenuation device here illustrated as a re- +a or p-a, in

sistance 24 may beprovidedto reduce the amount ofenerg fed back in case singing is troublesome. he high frequency modulated energy is similarly fed to the line 2 through c1rcuit 26 which includes the secondary 25, the filter E. and the attenuating resistance 27. T e terminal elements of filters F and F are paths of low impedance for currents of the frequencies passed by filters F and F respectively. 1 The arrangement il ustrated in Fig. 9

differs from that of Fig. 8 only in that a secondary .of the transformer 16 is connected to a divided circuit 22 for transferring both signaling'and carrier current energy.

The thermionic detectors, modulators and repeaters herein shown will ordinarily act as energy amplifiers and in general may be regarded as performing this function.

The novel features inherent in the invention are pointed out in the accompanying claims.

What is claimed is: A p

1. The method of duplex carrier wave telephony which comprises producing speech currents at each end of a system.

passing incoming and outgoing speech conveying wayes through identical conductive paths but in opposite directions throughout the entire system, and changing the frequency of transmitted waves during transmission.

2. A two-way low frequency line, a twoway high frequency line, means for interconnecting said lines comprising a telephone operators cord. circuit havin a source of carrier frequency oscillations serially included between the terminals thereof. 1 I 3. A telephone cord circuit for use in carrier current systems serially including a frequency selective device, a source of carrier current, and a second frequency selective device, in the order named.

4, A two-way low frequency line, a twoway high frequency line, means for intercinnecting sai lines comprising a telephone c rd circuit serially including a modulator carrier Waves.

i 5. A two-way low frequency line, a twoway high fr uency line, means for interconnecting saiii lines comprising a telephone cord circuit serially including a detector for detecting carrier waves. 1

6. A two-way low frequency line, a twoway high fr uency line, means for interconnecting said lines comprising a telephone cord circuit including a two-way conductin device constituting a modulaton-detector. A cord circuit containin itwo filters for transmitting different ranges of frequencies and a thermioniqdevice included therebetween. g M

8. A cord circuit, containing two band filters and a wave distorting device included therebetween.

9. A cii'cuit for signaling comprising a band filter for passing a high range of frequencies, a band filter for passing a low range of frequencies, and a symmetrically con ucting frequency-changing device connected between said filters.

10. A signaling system comprising a plurality of; signal frequency channels, a plu- 40 ralitv -ofg' connecting circuits each of which is ada tedjto be' connected to any selected one o- -'s aidjchannels, two-way conducting modulating-detecting means in each said circuit, andga two-way low frequency line and a two-way high frequency line adapted to be interconnected by said connecting circuits.

11. A duplex signaling system comprising two stations and a bidirectionally conducting modulator-detector device connected therebetween, said device serving as a modulator for signals passing in one direction and a detector for signals passing in the other direction.

12. A system comprising a source of alternating current, a plurality of pairs of thermionic devices connected to said source, the devices of each pair being oppositely poled with respect to said source, and another source of current with respect to whici the devices of each pair are similarly ole p 13. A circuit for use in transmission systems, comprising a band filter for passing a range of frequencies, a second band filter ifori passing a diflerent range of frequencies,

and a source of carrier frequency oscillations connected between said filters, said circuit comprising means for the transfer of energy in each direction therethrough.

14:. A wave transfer circuit, comprising an input circuit and an output circuit and a pair of separate as mmetricall conduct-- ing circuits o ilposite y connecte with respect to both t e input and output circuits, each of said last mentioned circuits including a lurality of space discharge paths.

15. wave transfer circuit, comprising a pair of input impedance elements, an incoming line including a source of waves to be transferred into said elements, and a local source of alternating current, each of said input impedance elements bein divided into two parts, and said iocal source being oppositely connected to the two parts of each thereof.

16. A system comprising a plurality of pairs of thermionic devices, a source of alternating current, and a second source of alternating current, said pairs of devices being'oppositely poled with respect to one of said sources and the individual devices of a pair being oppositely poled with respect to another of said sources.

17. A modulating system comprising a source of high frequency oscillations, a source of modulating oscillations, and an output path combined with a plurality of two-electrode thermionic devices connected to said sources b means whereby ure modulated oscillations are transferre to said output path and by means whereby the halves of the waves from said source of high frequency oscillations are symmetrically transferred.

18. A cord circuit for connecting two transmission circuits, said cord circuit containing two' filters for excluding difi'erent ranges of frequencies, and a thermionic device included in said circuit between said filters.

19. A telephone exchange system comprising a plurality of cord circuits each provided with selective means, one of said selective means being adapted to pass a different range of frequencies than others thereof, two-wa low frequency line and a twoway high requency line are adapted to be interconnected by any one of said circuits.

20. A telephone exchange system comprising a plurality of cord circuits each provided with a source 'of carrier waves serially included therein, at least one of said sources having a different frequency than others thereof, and at least one two-way high frequency line which may be connected for twoway communication by any one of said circuits to any telephone line terminating in said exchange.

21. In a carrier wave system a source of low frequency waves, means including a a 1,ue,ae7

modulating device for'stelilping u the frelatin means com rising means for reducing l quency of said waves to a igher equency, the equency o the received waves, and other means including a second modulatin said first mentioned modulating means comdevice for ste ping up the frequency of sai prising means for further reducin the free- 6 waves of big er frequency to a still higher quency of said waves of reduced r uency.

freguenc means for transmitting waves of In witness whereof, I hereunto su scribe sai hig est frequency, said transmitting my name this 26th day of August, A, D., means comprising means for receiving in- 1919. coining waves, said second mentioned modu- ELMER V. GRIGGS. 

